Given the SAS data set WORK.ONE:
| Id | Char1 |
| 111 | A |
| 158 | B |
| 329 | C |
| 644 | D |
and the SAS data set WORK.TWO:
| Id | Char2 |
| 111 | E |
| 538 | F |
| 644 | G |
The following program is submitted:
data WORK.BOTH;
set WORK.ONE WORK.TWO;
by Id;
run;
What is the first observation in SAS data set WORK.BOTH?
A.
| Id | Char1 | Char2 |
| 111 | A |
B.
| Id | Char1 | Char2 |
| 111 | E |
C.
| Id | Char1 | Char2 |
| 111 | A | E |
D.
| Id | Char1 | Char2 |
| 644 | D | G |
Answer: A
注解：SET statement的作用是将多个data set合并，但不会对观测值进行合并。题目中，新data set BOTH中将包含ONE和TWO中所有的变量，BY statement作用是使新data set根据ID升序排列，所以ONE中的第一条数据将成为BOTH中的第一条数据，由于该观测值中没有Char2变量，所以输出结果中显示为missing。完整的BOTH为：
| Obs | Id | Char1 | Char2 |
| 1 | 111 | A | |
| 2 | 111 | E | |
| 3 | 158 | B | |
| 4 | 329 | C | |
| 5 | 538 | F | |
| 6 | 644 | D | |
| 7 | 644 | G |
如需对观测值合并，应当使用MERGE，具体请参考SAS Base (28)。